Why Chromic Acid is using to clean the Glassware

chromic Acid
chromic Acid

In pharmaceutical laboratories, glassware is often cleaned using chromic acid due to its strong oxidizing properties and ability to remove organic contaminants and Heavy stains on glass.

Why Chromic Acid is used for cleaning of Glassware in Quality Control Laboratory :

Below are the reasons to use of chromic acid for cleaning of Glassware :

  1. Stain Removal/Difficult-to-Remove Substances : It is particularly effective at removing stubborn stains on glassware, such as those caused by dyes, pigments, or chemical reactions. The acid’s strong oxidizing nature allows it to react with and break down these stains, restoring the glass to its original clarity.
  2. Organic Residue Removal: It can react with and oxidize organic compounds present on glassware, such as oils, greases, and other organic residues. This helps to break down and remove these substances from the glass surface
  3. Inorganic Residue Removal: It can also remove certain inorganic residues, such as mineral deposits and metal oxides, which may accumulate on glassware over time. The acid’s oxidizing properties aid in breaking down these deposits, facilitating their removal.

Way to use Chromic Acid for Glassware cleaning : 

Procedure to make the solution of Chromic Acid in laboratory  :

It is a mixture prepared by dissolving 200 gm of sodium dichromate in about 100 ml of water, cooling in an ice bath and adding slowly to it, with stirring, 1500 ml of sulphuric acid. The mixture should be prepared in a hard borosilicate glass beaker and safety glasses must be used during the addition of acid.

Procedure To clean the Glassware with Chromic Acid :

  • Fill the stained glassware with chromic acid cleaning solution. Keep for at least 30 minutes.
  • Pour the chromic acid cleaning solution back into its original bottle. It can reuse repeatedly until a green color develops, indicating that the solution is spent and should no longer be used.
  • Rinse the glassware thoroughly with sufficient quantity of potable water.
  • Wash the glass ware with 1 %  soap solution and rinse glass wares thoroughly with Potable water.
  • Finally rinse with Purified water.
  • Dry it in hot air oven at 60°C.

Note : 

  1. It  should not be used for cleaning of calibrated containers used for optical measurements.
  2. It is highly toxic and corrosive. Use gloves, mask and safety goggles while handling it.


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